Phosphors of the oxynitridosilicate type are known per se under the shortened formula MSiON; cf. for example “On new rare-earth doped M-Si—Al—O—N materials”, J. van Krevel, TU Eindhoven 2000, ISBN 90-386-2711-4, Chapter 6. There, they are doped with Tb. Emission is achieved under excitation by 365 nm or 254 nm.
A new type of phosphor is known from EP patent 1 449 264, ,which corresponds to U.S. Ser. No. 10/496,560. It consists of Eu or Eu, Mn-coactivated oxynitridosilicate of formula MSi2O2N2 (M=Ca, Sr, Ba)
The basic structure of the host lattice is known from “Phase Relationships in the Sr—Si—O—N system”, W. H. Zhu et al., J. Mat. Sci. Lett. 13 (1994), pp. 560-562, where it is discussed in conjunction with ceramic materials. In this reference, it was established that this structure occurs in two modifications, namely a low-temperature phase X1 and a high-temperature phase X2. The low-temperature phase, referred to below as LT for short, is produced predominantly at approximately 1300° C., whereas the high-temperature phase, referred to below as HT for short, is increasingly produced at higher temperatures up to approximately 1600° C. However, the two phases are fundamentally difficult to separate, since they have the same basic structure but different lattice constants. The exact stoichiometry of the two phases may deviate from the formula MSi2O2N2.